Healthcare-v2009 IEQc8.1: Daylight and views - daylight

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  • USGBC

    Excerpted from LEED 2009 for Healthcare

    IEQ Credit 8.1: Daylight and views - daylight

    Intent

    To provide building occupants with a connection between indoor spaces and the outdoors through the introduction of daylight and views into the regularly occupied areas of the building.

    Requirements

    Install daylight responsive controls in 100% of the area that meets the daylight quantity thresholds above. Daylight controls must switch or dim electric lights in response to the presence or absence of daylight illumination in the space.

    For a minimum of 75% or more of the perimeter area used to qualify under IEQ Credit 8.2, achieve daylighting in at least the following spaces1, through 1 of the 4 options:

    OPTION 1. Simulation

    Demonstrate through computer simulations that 75% or more of perimeter area used to qualify under IEQ Credit 8.2 achieve daylight illuminance levels of a minimum of 10 footcandles (fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter. 2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter.) and a maximum of 500 fc in a clear sky condition on September 21 at 9 a.m. and 3 p.m.

    Provide glare control devices to avoid high-contrast situations that could impede visual tasks. However, designs that incorporate view-preserving automated shades for glare control may demonstrate compliance for only the minimum 10 fc illuminance level.

    Option 2. Prescriptive

    For sidelighting zones:

    • Achieve a value, calculated as the product of the visible light transmittance (VLT) and window-to-floor area

      ratio (WFRWindow-to-floor ratio (WFR) is the total area of the window (measured vertically from 30 inches above the finished floor to the top of the glass, multiplied by the width of the glass) divided by the floor area.) between 0.150 and 0.180.

    • 0.150 < VLT x WFR < 0.180



    • The window area included in the calculation must be at least 30 inches (0.8 meters) above the floor.
    • In section, the ceiling must not obstruct a line that extends from the window-head to a point on the floor that is located twice the height of the window-head from the exterior wall as measured perpendicular to the glass (see diagram on the next page).





    • Provide glare control devices to avoid high-contrast situations that could impede visual tasks. However, designs that incorporate view-preserving automated shades for glare control may demonstrate compliance for only the minimum 0.150 value.

    For toplighting zones:

    • The toplighting zone under a skylight is the outline of the opening beneath the skylight, plus in each direction the lesser of (see diagram below):

      • 70% of the ceiling height
      • 1/2 the distance to the edge of the nearest skylight
      • The distance to any permanent partition that is closer than 70% of the distance between the top of the partition and the ceiling.



    • Achieve skylight coverage for the applicable space (containing the toplighting zone) between 3% and 6% of the total floor area.
    • The skylight must have a minimum 0.5 VLT.
    • A skylight diffuser, if used, must have a measured haze value of greater than 90% when tested according to ASTMVoluntary standards development organization which creates source technical standards for materials, products, systems, and services D1003.
    OPTION 3. Measurement

    Demonstrate through records of indoor light measurements that a minimum daylight illumination level of 10 fc and a maximum 500 fc has been achieved in at least 75% of the perimeter area used to qualify under IEQ Credit 8.2. Measurements must be taken on a 10-foot grid for all occupied spacesEnclosed space intended for human activities, excluding those spaces that are intended primarily for other purposes, such as storage rooms and equipment rooms, and that are only occupied occasionally and for short periods of time. Occupied spaces are further classified as regularly occupied or nonregularly occupied spaces based on the duration of the occupancy, individual or multioccupant based on the quantity of occupants, and densely or nondensely occupied spaces based on the concentration of occupants in the space. and recorded on building floor plans.

    Provide glare control devices to avoid high-contrast situations that could impede visual tasks. However, designs that incorporate view-preserving automated shades for glare control may demonstrate compliance for only the minimum 10 fc value.

    OPTION 4. Combination

    Any of the above calculation methods may be combined to document the minimum daylight illumination in at

    least 75% of the perimeter area used to qualify under IEQ Credit 8.2.

1 Comments

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Christie Morris-Withers NIKA
Mar 20 2017
LEEDuser Member

LEED HC 2009 - IEQc8.1 Daylight

Project Location: United States

In order to get this credit it appears that all windows with "high-contrast situations" must have glare control devices. Are these devices also required to be view-preserving and automated? Are manual aluminum blinds acceptable?

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Mar 29 2017
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